Due to increased environmental consciousness, the concept of using vegetable oil as a fuel has developed in recent years. In Malaysia, biodiesel has been successfully derived from palm oil. Patent No. PJ1105/88 has revealed a process of producing palm oil methyl esters (palm diesel) from palm oil. Palm oil is converted into palm oil methyl esters via transesterification and the derived palm oil methyl esters or palm diesel have proven to exhibit good fuel properties and are able to be used as a diesel substitute. ‘Production and Evaluation of Palm Oil Methyl Esters as Diesel Substitute’ published in Elaeis Special Issue, November 1995, pp 15-25 discloses the fuel characteristics of palm diesel and also its potential to be used as a diesel substitute.
However, palm oil methyl esters being evaluated of having pour point of +15° C. to +18° C. has a limitation to its usage or consumption as a fuel especially in cold climate countries. Although palm diesel exhibits good fuel properties and able to meet the fuel specifications, some problems arise when it is used in low operational temperature. This is because the pour point of palm oil methyl esters is +15° C. to +18° C. Pour point is the temperature of the oil 3° C. above the point at which the test sample will not move when tipped out of the horizontal.
The fluidity of a fuel in an engine or machine is very important under all circumstances. When starting up an engine from cold, it is vital that the mechanical parts are able to move freely and there is no difficulty in transporting the fuel through lines and pumps. Failure to do so will lead to blockage and the engine or machine may become inefficient and inoperable.
When fuel is cooled to low temperature, it can undergo a number of changes, namely solidification, solidification with the formation of a precipitate of macrocrystals and solidification with the formation of microcrystals, which swell, giving a crystalline structure that traps the remaining oil. Under these environments, restriction in the flow of the fuel occurs. Thus, good low temperature flow characteristics (pour point) of a fuel is essential to ensure smooth operation and to be suitable for various applications. A fuel is necessary to have good pour point, which is the temperature of the oil 3° C. above the point at which the oil will not move when tipped out of the horizontal. The pour point of all samples were analysed using standard method ASTM D97. The pour point should be below the operational temperature.
To improve the low temperature characteristics mentioned earlier, pour point depressants are normally employed. They act through surface adsorption on to the wax crystals. The resulting surface layer of the pour point depressant inhibits the growth of the wax and paraffin crystals. Thus, in the absence of long inter-locking crystals or swollen particles, fuel can move freely. However, these additives though blended into the fuel in small quantity, they are costly.